[Gmecm] Converting eprom to eeprom problem

[Rick McLeod]

That should work fine, relatively 4.7K is a low
impedance to an EEPROM input, especially if you bypass
it w/ a small ceramic cap of say .001



--- bcroe at juno.com wrote:

> I am wondering how you get a high and a low with dip
> 
> switches, which are single pole single throw (and
> not 
> always reliable).  The usual way is use about a 4.7K
> 
> resistor between the input and VCC for a high.  Then
> 
> short the input to gnd with a switch for a low.
> Bruce Roe
> 
> 4 Oct 2005  Rick McLeod <dunvegan at sbcglobal.net>
> writes:
> > Why would you not just use signal ground as the
> logic
> > level low, I've done that for years when I had a
> > bigger address buss than I needed/could address,
> which
> > is your scenario. VCC and SigGND switched w/ dip
> > switch should work just fine. What about the rest
> of
> > the signals for the EEPROM, make sure you have
> tied
> > the program/erase lines to the appropriate levels.
> The
> > action you are getting makes me think (I'm not
> sure of
> > the code in the ECM you have) that it is checksum
> > error'ng, is the program you are using fouling the
> > checksum bits, or is this even appropriate for
> your
> > ECM, I'm not sure, just an idea.
> > 
> > Your approach is sound, Moates has been doing that
> w/
> > other ECM/PROMs as I recall, might check his site
> for
> > some insight.
> > 
> > Good luck!
> > 
> > 
> > --- Darryl M Gilbert <dgilbert78 at juno.com> wrote:
> > 
> > > Hmmmmm, should work. Do you have a bypass cap
> > > between Vcc and gnd right
> > > at the chip?? I would have to look at the chip
> specs
> > > to see whats up, but
> > > sounds logical. Make sure when you switch from
> one
> > > to the other no pins
> > > are left floating, you know, not connected to
> > > anything. All pins should
> > > be terminated, never floating
> > > good luck
> > > darryl..
> > > On Tue, 04 Oct 2005 20:05:33 -0500 Mike Poore
> > > <mp at FlowersByValerie.com>
> > > writes:
> > > > I have an '870 ecm that has a 2732 eprom. My
> goal
> > > was to make a new 
> > > > board that I would allow me to use a 2864
> eeprom.
> > > I have soldered in 
> > > > a 
> > > > new dip socket and remotely located the
> (e)eprom
> > > to a new board with 
> > > > dip 
> > > > switches to allow for using a 2732 or the
> 2864.
> > > The dip switches are 
> > > > 
> > > > configured to allow usage of the lower 32k or
> > > upper 32k of the 2864 
> > > > 
> > > > thereby tricking the ecm to think a 2732 is
> > > installed.
> > > > 
> > > > My theory is that if I could provide either a
> high
> > > or low signal to 
> > > > A12 
> > > > (pin 2 on the 2864), via the dip switches,
> then
> > > the ecm would 
> > > > address 
> > > > A0-A11 as normal. That would then allow the
> 2864
> > > to be split into 
> > > > banks 
> > > > of 32k.
> > > > 
> > > > I have run tests and the 2732 works fine, so I
> > > know that there are 
> > > > no 
> > > > problems with noise or wiring of the circuit
> in
> > > this configuration. 
> > > > I 
> > > > copied the same bin to the lower half of the
> 2864.
> > > To provide high 
> > > > and 
> > > > low signals to A12 of the 2864 to read the
> 2864, I
> > > used Vcc (pin 24) 
> > > > of 
> > > > the 2732 socket connected to A11 (pin 2) of
> the
> > > 2864 to provide a 
> > > > high 
> > > > signal and used a low signal from Chip Enable
> (pin
> > > 18) of the 2732 
> > > > socket.
> > > > 
> > > > Using the above circuit, the ecm works very
> > > briefly and then the ses 
> > > > 
> > > > light starts blinking very quickly, which
> seems to
> > > indicate a memory 
> > > > 
> > > > problem. That low signal from the Chip Enable
> > > circuit seems to be a 
> > > > problem.
> > > > 
> > > > Before going any further, can anyone offer an
> > > opinion as to wether 
> > > > the 
> > > > Chip Enable pin is a reliable low signal
> source,
> > > and if not, suggest 
> > > > a 
> > > > better way to get a low signal to A12. I have
> not
> > > tried using the 
> > > > upper 
> > > > 32k yet, so I am also very interested in any
> > > opinions on using Vcc 
> > > > as a 
> > > > high signal for A12.
> > > > 
> > > > I am an electronics novice, so if you have a
> > > solution, please be 
> > > > detailed. For example, if you told me I need a
> > > pull-up resistor, I 
> > > > know 
> > > > the principle behind it, but could not figure
> out
> > > how to include it 
> > > > in 
> > > > my circuit. In other words, I know enough to
> be
> > > dangerous.
> > > > 
> > > > Thanks, Mike
> > > >
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